Wrong type is shown in tooltip of custom not in scene tree

[RedwanFox]

Godot version:
Godot 3.1 RC3

OS/device including version:
MacOSX 10.14.3

Issue description:
In editor in scene tree if user adds registered class node, tooltip will show base class as type.

Steps to reproduce:

1. Create script.
2. Register it as class.
3. Add node of this class to scene.
4. Loot at the tooltip.

Minimal project

extends Node

class_name MyCustomNode

func _ready():
    pass

[bojidar-bg]

Strongly related to #6067. Custom node types are just shortcuts for assigning a script to a node of the base type.

[aaronfranke]

See also: #16863 (comment)